The Universal Mobile Telecommunication System (UMTS) is one of the third generation mobile communication technologies designed to succeed GSM and 3GPP Long Term Evolution (LTE) is a project within the 3rd Generation Partnership Project (3GPP) to improve the UMTS standard. UMTS Terrestrial Radio Access Network (UTRAN) is the radio access network of a UMTS system and evolved UTRAN (E-UTRAN) is the radio access network of an LTE system. In UTRAN, the User Equipments (UE) are wirelessly connected to the radio base stations denoted NodeBs (NB) and the NBs are controlled by Radio Network Controllers (RNC). The RNCs are further connected to the core network. However, the radio base stations in E-UTRAN are called evolved NodeB (eNB) and the eNBs are connected directly to the core network.
In UTRAN, each UE is configured with different configurations associated with resource management. Examples of such a configuration are scheduling configuration, MIMO (Multiple Input Multiple Output) configuration, measurement configuration and DRX configuration. Hence, the UE is e.g. given one specific scheduling configuration and the UE should behave in a certain way when it receives a scheduling command based on the scheduling configuration.
In E-UTRAN, it is desired to be able to handle a plurality of configurations associated with the same type of radio resource management. E.g. it would be desired to be able to handle a plurality of scheduling configurations and to switch between the plurality of different scheduling configurations. The existing procedure to reconfigure a single configuration with RRC (radio resource control) procedures would be too slow when more than one configuration is used.
More specifically, there is a need to configure and re-configure multiple configurations in a UE, such that switching between the configurations can be made in a quick manner.
Furthermore, in UTRAN synchronized re-configuration of radio resource related configurations are handled by using an activation time. I.e. an activation time which is a reference to a certain connection frame number (CFN) is included in a radio resource control (RRC) protocol message (which is a higher protocol layer message) in order to assure that the UE starts using the new configuration at the same time instance as the Node B. Since the RRC message may be subject to retransmissions on a lower protocol layer, the activation time must be set far enough into the future to allow for retransmissions of the message. Even if the average retransmission delay is small there are a few percent of the messages that needs several retransmissions. The activation time needs to be set to cover also the worst case which leads to that synchronized re-configuration in UTRAN causes a relatively long delay. It has been a desire in E-UTRAN to avoid these delays.
Another undesirable consequence of the activation time in UTRAN is the fact that the execution of an RRC procedure in the UE may take considerable time. Therefore, in UTRAN RRC, it has been necessary to specify the handling of several parallel ongoing procedures in the UE. This issue has resulted in a lot of complexity in the specifications.
Due to these drawbacks, there is a strong desire to avoid the “activation time solution” in the RRC specification for E-UTRAN.
Examples of RRC configurations that may require synchronization between the UE and the radio base station are scheduling, MIMO parameters, switching of CQI reporting.